College Park, MD -- Urban soils provide extensive ecosystem services that properly regulate the surrounding environment for all living organisms. Nutrient management, water purification, and plant growth are on the short list, but can become compromised by urbanization. To understand the deeper effects of urbanization on city soils, a team of researchers including Stephanie Yarwood, associate professor in UMD’s Environmental Science and Technology department have published a first-of-its-kind study examining microbial communities in these soils within five different cities. Results uncovered an alarming decrease in ectomycorrhizal fungi, an important organism that enhances plant growth and improves overall health of soils through stabilization and aggregation. This study offers clear evidence of how human urbanization may lead to a decline in diversity of unique populations of microbes on a global scale, in some cases those that have profound implications for human quality of life.

The absence of ectomycorrhizal fungi in soils makes it difficult for trees to establish in urban locations, causing nutrient deficiencies that may require the addition of synthetic fertilizers. As more people move into cities, recent research suggests that human health is improved when the city includes abundant greenspace. Trees are fundamental to improving air quality and are proven locations for folks to relieve stress.

Furthermore, through an examination of the biogeography (distribution of species among different geographical areas) of microbial communities, Yarwood determined that there are unique local populations of ectomycorrhizae. Due to the overall decrease in these organisms combined with the existence of aforementioned local populations, she and her graduate student are able to conclude that urbanization contributes to a loss of global biodiversity.

“We are excited to unveil this first-ever comparison of five cities on three continents to report an important, impactful global trend, vs. a single study and location which has been tackled in the past,” said Stephanie Yarwood, PhD of UMD’s College of Agriculture and Natural Resources. “This study demonstrates the need to maintain viable soil and plant areas that continue to serve as natural habitats for microorganisms such as ectomycorrhizae. At its core, this is a human health issue, and we hope our research influences city residents to become more aware of the importance of improving their soils.”

To facilitate this widespread understanding of the effects of urbanization on microbial communities, Yarwood and her team collected samples as part of the Global Urban Soil Ecological Education Network, which, as its website explains “develops experimental protocols that are simple to adopt across many habitat types and soil conditions in urban areas across the world”. This represents an innovative grassroots effort to coordinate international research about the effects of urbanization on microbial communities, one that Yarwood hopes will serve as a model for valuable new insights into emerging global trends.

In collaboration with researchers from USDA Forest Service, Johns Hopkins University, University of Helsinki, North-West University (South Africa), University of Veterinary Science (Budapest) and the Hungarian Academy of Sciences, Yarwood recently completed a manuscript titled “Urbanization">https://www.nature.com/articles/s41559-017-0123">Urbanization erodes ectomycorrhizal fungal diversity and may cause microbial communities to converge” which was published in the journal Nature Ecology and Evolution.